This invention relates to an automatic combinational weigher adapted for multiple operations such that not only article batches with different target weight values but also articles of different kinds can be weighed simultaneously and more particularly to such a combinational weigher with a single computer for controlling its mutually independent operations. Additionally, this invention relates to certain new methods of efficiently operating such a weigher.
Combinational weighing means weighing articles by a plurality of weighing devices, performing arithmetic operations for combinations of weighed values and then selecting a combination according to a predetermined criterion. Its basic principle has been known and many combinational weighers of different types have been described in issued patents and commercially made available. U.S. Pat. No. 4,708,215 assigned to the present assignee, for example, discloses a computerized automatic combinational weigher of a popular type having a number of circularly arranged article batch handling units. Articles which are to be weighed may be transported by a conveyer belt and dropped onto an article feeding unit at the center and distributed thereby to the individual article batch handling units. Each article batch handling unit is provided with hoppers including one for weighing the article batch delivered to the unit and the weight values of the measured article batches are communicated to a control system such as a computer. The computer is programmed not only to compute combinations of these weight values and to select a combination according to a predetermined criterion such as the combination giving a total weight within a preselected range, but also to discharge the article batches from the selected article batch handling units for packaging. U.S. Pat. No. 4,694,920 assigned to the present assignee, for example, discloses a control unit for a combinational weigher of this type characterized as having a multi-computer structure such that many adjustments and modes of operation can be made available.
Automatic combinational weighers of this and most other types are operated primarily for weighing one kind of article at a time by setting a target weight value. If it is desired to weigh two or more different kinds of articles or if there are two or more target values for articles of the same kind, such as when 50 g, 100 g and 200 g packages of identical articles are desired, the weigher must be reset after a desired number of article batches of each type has been discharged. Alternatively, two or more weighers may be mobilized concurrently, each operating with different articles and/or a different target value. The first alternative would adversely affect the work efficiency, while the second alternative would require extra conveyer belts and other accessory units and the entire operation becomes complicated. Japanese Patent Publication Kokai No. 60-183831 discloses an automatic combinational weigher adapted for twin operations, that is, for weighing articles of the same kind concurrently with two different target weight values. If each article batch handling unit is provided with its own computer for its control as taught in U.S. Pat. No. 4,694,920, however, problems arise when the grouping of the article batch handling units for the two operations is changed. If the target weight value of the second group is to be varied according to the result of measurements by the first group, furthermore, transfers of data between the computers become time-consuming. U.S. Pat. Nos. 4,522,274, 4,549,619 and 4,658,920 assigned to the present assignee, for example, disclose technologies of using one computer to control a plurality of article batch handling units having the same operation cycle but it has not been known to control a plurality of article batch handling units for multiple non-synchronous operations by a single computer.